1. Field of the Invention
This invention relates generally to the field of combinating tumbler locks, and more particularly to panel mounted tumbler locks for electrical equipment.
2. Description of the Prior Art
There are many locking applications where an inexpensive and reliable combinating tumbler lock is desired. Many such combinating tumbler locks are in the prior art. However, many of these have drawbacks which make them undesirable as they are either too expensive or do not give adequate performance.
A common problem with combinating tumbler locks is a rough operation between various stopped positions, illustratively the locked and unlocked positions. This rough operation makes these locks inconvenient to use and also can result in difficulty in locating the various stops. In electrical applications, where the lock is used to actuate a switch, such difficulty in positioning can lead to the undesirable result that the switch will not be actuated at the position where the operator expects actuation. This rough operation is usually a result of frictional contact between the lock plug, which houses the combinating tumblers, and the lock shell.
One solution to rough operation is to increase the clearance between the plug and the shell. This increased clearance, however, can lead to undesirable play between the plug and shell. Further, this clearance can lead to security problems, as the lock becomes subject to pull out as well as punch out.
The problem of inaccurate positioning is often solved by engageable detents on the lock plug and lock shell. These detents are arranged such that they will engage when the shell is rotated to a particular stop position, thereby preventing further rotation of the plug and providing accurate positioning. However, such detents limit the adaptability of the lock to various applications. Often, electrical switch locks have more than one stop position, which is not compatible with the use of detents. Further, use of detents means that the lock has a preferred orientation. If the application requires a twelve o'clock locked position and a three o'clock unlocked position, the lock with detents must be oriented accordingly. This can lead to delay, inaccuracy and inconvenience in installation. It would thus be desirable to have a lock that provides for accurate stop positioning but that allows for more than one stop position and does not have a preferred orientation.
As with all locks, ease of construction and assembly are desirable features; as is inexpensive cost of manufacture and resistance to tampering.